The present invention relates to a method for connecting user terminals to one another over a network containing a plurality of user-terminals and a respective plurality of network access servers, and also relates to a network access server and subscriber data service for implementing such a method. The invention further relates to a user terminal included in such a network, and to software running on the processing systems in the subscriber data service or the user terminal for implementing the method.
Such a method for connecting a first user-terminal to a second user-terminal is already known in the art, e.g. from the internet draft document “A FRAMEWORK FOR IP BASED VIRTUAL PRIVATE NETWORKS” from the authors Bryan Gleeson et al, published in February 1999 by the Internet Engineering Task Force (IETF). Therein, a virtual private network is constituted by configuring all network access server access links, called stub-links in the referred draft, with the identity of the particular virtual private network whereto the access link of the network access server belongs.
In this way each user-terminal is assigned to a particular virtual private network in a static way. Each of the user-terminals assigned to a common virtual private network are able to establish a communication with any other user-terminal assigned to the same virtual private network because information on the address of each connected user-terminal, called reachability information is available within the virtual private network.
At the moment there is a first user-terminal being assigned to a first virtual private network willing to establish a communication with a second user-terminal being assigned to a second virtual private network there is no way of connecting both user-terminals in order to establish a communication because there is no information available on the address of the second assigned to the second virtual private network.
An object of the present invention is to provide a method of the above known type, a system, a network access server, a subscriber data server and a second user-terminal adapted to perform this method, but wherein access from a first user-terminal connected to a first virtual private network is able to connect to a second user-terminal connected to a second virtual private network.
According to the invention, this object is achieved by a method for connecting a first and second user terminals to one another over a network (e.g., the internet) containing a respective plurality of network access servers, characterised in that a subscriber data server is added to the network and that the necessary connection information is made available enabling determination of the location of the second (i.e., to be connected) user-terminal. The subscriber data server is able to store and retrieve information as to which network access server the second user-terminal is connected to and the virtual private network the second user-terminal forms part of. At a connection request from a user-terminal forming part of a different virtual private network, the subscriber data server retrieves the connection information about the second user-terminal in order to locate this user-terminal. Subsequently, the subscriber data server forwards a connection request to the located second user-terminal. The second user-terminal in its turn decides on accepting the incoming call. If the incoming call is accepted, the second user-terminal forwards a request to the network access server it is connected to, to switch its connection from its current virtual private network to the first virtual private network. At the moment the switch is performed, both user-terminals form part of the same virtual private network. Then they are able to establish a communication because address information of the second user-terminal is available and accessible for the first user-terminal in this context.
The invention further resides in a network access server, subscriber data server and second user terminal configured to perform the above-described method.
Another characteristic feature of the present invention is that the connection request of the first user-terminal may be sent from.